Orthodontic screw-type device and method of making same

ABSTRACT

An orthodontic screw-type biassing device comprises: a first member having an internally threaded bore, the threaded bore comprising first and second threaded portions adjacent each other in the axial direction of the bore, the first and second threaded portions having thread roots which lie substantially on a common line, the first threaded portion having threads of given depth and the second threaded portion having threads of a lesser depth. A threaded inner screw-type member is threadably engaged in the internally threaded bore of the member, the threads at an end portion of the inner screw member being deformed so as to freely, threadably pass through the second threaded portion of the threaded bore and to bind and be non-rotatable in the first threaded portion of said threaded bore. The invention is also directed to a method of making such a biassing device.

BACKGROUND OF THE INVENTION

This invention relates to an orthodontic screw-type biassing device, andmore particularly to such a device including means for preventing thescrews from being disengaged from their threaded receptacles.

Screw-type orthodontic devices have been known for many years, one suchtypical device being illustrated in U.S. Pat. No. 3,832,778 to M.Wallshein. Recently, multi-screw devices, using nested screwarrangements, have been developed, such as those disclosed in U.S. Pat.No. 4,107,843 and in U.S. application Ser. No. 785,587, filed Apr. 7,1977 by Mr. Wallshein. The entire contents of U.S. Pat. No. 4,107,843and of U.S. patent application Ser. No. 785,587 are incorporated hereinby reference. A problem in the art of designing and fabricatingscrew-type actuators for orthodontic biassing elements is to prevent thescrews from being disengaged from their respective threaded receptables.In the multi-screw arrangement of U.S. Pat. No. 4,107,843, ashoulder-stop arrangement is provided to prevent the larger screw fromcoming out of its body housing, but there is no means provided forpreventing the smaller screw from becoming disengaged from the largerscrew. Patent application Ser. No. 785,587 shows various differentconstructions for preventing disengagement of the screws, both the largescrews and the small screws, from their respective threaded receptaclesto prevent inadvertent disassembly of the device in the mouth.

The object of this invention is to provide a simplified and easy tomanufacture construction for preventing threaded screws from becomingdisengaged from their threaded receptacles.

SUMMARY OF THE INVENTION

According to the present invention, an orthodontic screw-type biassingdevice comprises: a first member having an internally threaded bore, thethreaded bore comprising first and second threaded portions adjacenteach other in the axial direction of the bore, the first and secondthreaded portions having thread roots which lie substantially on acommon line, the first threaded portion having threads of given depthand the second threaded portion having threads of a lesser depth. Athreaded inner screw-type member is threadbly engaged in the internallythreaded bore of the first member, the threads at an end portion of theinner screw member being deformed so as to freely, threadably passthrough the second threaded portion of the threaded bore and to bind andbe non-rotatable in the first threaded portion of said threaded bore.

The invention is also directed to a method of making such a biassingdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first embodiment of the invention as applied to asingle-screw device;

FIG. 2 illustrates a second embodiment of the invention as applied to anested screw device;

FIG. 3 illustrates a method of fabricating a screw-type device of thepresent invention; and

FIG. 4 illustrates a further embodiment of the invention as applied to anested screw device.

DETAILED DESCRIPTION

Referring to FIG. 1, which illustrates a single-screw type biassingdevice, the threaded actuator screw 1 is threadably engaged in a bodyhousing 2, the threaded actuator screw having an engagement spindleportion 3 with holes 4 therein for engagement by an actuator, such as arod or pin-shaped actuator. The screw 1 is threaded along the completelength thereof, the portions 1a and 1b being oppositely threaded withrespect to each other. The end turns of the screw are "turned over" or"hammered down", or otherwise deformed, for example as illustrated at 5.The deformed end turns are normally deformed so that they bind and donot freely turn in the normally threaded portion 6 of the body housing2. The threaded portion 6 of the body housing 2 is ground down, orotherwise reduced in thread depth, so that the crests of the threadsthereof are shortened over the portion 6b of the threaded portion 6. Thethreads over the portion 6a remain intact. The turned down end threads 5of the threaded member 1 are deformed such that they pass freely throughthe area 6b of the threaded portion 6, but bind on the unalteredthreaded portion 6a so as to prevent further rotation of the threadedmember 1 relative to the body housing 2. This construction results in aneasy to manufacture, reliable arrangement to prevent the threadedactuator screw 1 from becoming inadvertently disengaged from thethreaded portion 6 of the body housing 2.

FIG. 2 illustrates a nested screw configuration for a biassing deviceaccording to the present invention. The body housing 12 has anunthreaded bore 21 therein which terminates at a shoulder 18 and athreaded portion 19. The outer screw 17 is threaded on its outerperiphery so as to mesh with threads 19 of the body housing 12, theouter screw 17 further having a flange or abutment portion 20 which,when the screw 17 is threaded out of the body housing, abuts againstshoulder 18 to serve as a stop to prevent disengagement of the screw 17from the body housing 12. The inner surface of outer screw 17 hasthreads 16 thereon, substantially the same as threads 6 of FIG. 1.Threads 16 comprise completely threaded portions 16a and threadedportions 16b wherein the crests of the threads have been ground orotherwise reduced in size. The inner screw 11 has a threaded portion 11aand an oppositely threaded portion 11b on opposite sides of the spindle13. The end turns of the screw 11 are turned down or otherwise deformed,as indicated at 15, so that the turned down end turns 15 may freely passthrough the reduced threads 16b, but bind or otherwise interfere withthe fully threaded portions 16a of the outer screw 17. Thus, this servesas a stop to prevent complete unthreading of screw 11 from the innerthreads 16 of screw 17.

The roots of threads 6a, 6b (and also threads 16a, 16b) lie on a commonline (i.e., they have a common major diameter d). The thread depth,i.e., the distance between the root and crest, is less in the portion 6b(and also 16b) than in the portion 6a (and 16a). That is, the threadedportions 6a and 6b have different minor diameters.

FIG. 3 illustrates a member 27 which is threaded on the outer surfacethereof and which has a bore 28 formed therein. A rotatably driven tool30 has a forward tapping portion 31 which cuts threads in the inner bore28 of member 27. The tool 30 has a rear cutting or milling-type portion32 which cuts the peaks off of the threads which are cut on the innersurface of member 27 by the tapping portion 31. Therefore, in oneoperation, the completely threaded portions 16a and the reduced crestthreaded portion 16b of the member 17 in FIG. 2 is formed. In use, thetool 30 is passed into the bore 28 sufficiently so that the rear cuttingportion 32 does not damage the forward threaded portion 16a (FIG. 2). Inthis manner, the member 27 is formed into the member 17 of FIG. 2.

As an alternative method of FIG. 3, a tool could be provided similar tothe tool of FIG. 3, but with a drill bit-type tip at the forwardmost endthereof. In this case, the member 27 need not have the bore 28pre-formed therein. By using such a composite tool, the bore is firstdrilled, the tap which is rearward of the drill taps the interior andthe cutting surface which is rearward of the tap cuts down the crests ofthe formed threads.

While FIG. 2 illustrates an arrangement wherein the present invention isused to prevent an inner screw 11 from becoming disengaged from an outerscrew member 17, the inventive concept may also be applied to preventthe outer screw of a nested screw arrangement from becoming disengagedfrom the body housing member, for example as illustrated in FIG. 4. Asshown in FIG. 4, a body housing 42, which is preferably similar in shapeand function to the body housings shown in U.S. Pat. No. 3,832,778 andin U.S. application Ser. No. 785,587, has a threaded bore 46 whichcomprises fully threaded portions 46a and threaded portions 46b with thecrests of the threads removed, such as in threaded sections 6b and 16bin FIGS. 1 and 2. An intermediate threaded member 47 is threadablyengaged in the threaded bore 46 with the outer threads thereof beingfull depth threads which normally fully engage the internally threadedportion 46a of the body member 42. The end turns or threads 45 of theintermediate member 47 are turned down or otherwise deformed asindicated at 45 so that the deformed portion 45 is threadably passablethrough the threaded portion 46b, but binds in the fully threadedportion 46a, thereby preventing the intermediate member 47 from beingfully unthreaded from the body member 42. The embodiment of FIG. 4 alsocomprises an inner threaded member 11 which may be substantiallyidentical with the inner threaded member 11 of FIG. 2. Intermediatethreaded member 47 preferably has internal threads thereon identicalwith threads 16a, 16b in FIG. 2, the end turn of threaded inner member11 being turned down, such as at 15 in FIG. 2.

Alternatively, the inner threaded member 11 of FIG. 4 may be threaded ina normally threaded internal bore of intermediate member 47 and othermeans may be provided for preventing the inner thread 11 from becomingdisengaged from the inner threads of intermediate member 47.

It should be clear that the various alternative arrangements of thepresent invention can be used in any combination, as desired, to preventthe respective screws from becoming inadvertently disengaged from theirrespective threaded receptacles. In FIG. 4, as in FIGS. 1 and 2, onlyone side of the device is illustrated. Preferably, the device is usedwith a body housing, or the like, on respective opposite sides of thespindle 13 so that the device may apply a spreading action in the mouthof a patient as the spindle is turned to rotate the oppositely threadedportions on the respective opposite sides thereof.

In a preferred embodiment of the invention, the thread depth of thethreaded portion 6b (and also 16b and 36b) is approximately 50 percentof the depth of the threaded portion 6a (and also 16b and 36b). Thisratio, however, is not limiting --other ratios between 30 and 70 percentshould also provide satisfactory results. The crests of the threads ofthe portions 6b, 16b and 36b are preferably substantially flat since thecreasts are formed by grinding or otherwise removing material from theoriginally formed screw threads with a rotary type tool. The threads 6a,6b (and also 16a, 16b and 36a, 36b) have a substantially common pitch,common thread angle and common major diameter d. The screw-type members1, 11, 17 and 47 are formed so as to mate with their respective threadedreceptacles using conventional dimensional tolerances as our standard inthe screw art. While the threads are shown as "V" threads, otherthreads, such as square threads, trapezoidally formed threads, buttressthreads, knuckle threads, etc. could be used on the mating threadedparts. Regardless of the type of thread used, the general criteriadiscussed hereinabove regarding depth of thread over the differentportions 6a, 6b; 16a, 16b; and 36a, 36b applies.

While the invention has been described above with respect to specificembodiments and specific methods of manufacture, it should be clear thatvarious modifications and alterations to the apparatus and method may bemade within the spirit and scope of the appended claims.

I claim:
 1. An orthodontic screw-type biassing device comprising:a firstmember having an internally threaded bore, said threaded bore comprisingfirst and second threaded portions adjacent each other in the axialdirection of said bore, said first and second threaded portions havingthread roots which lie substantially on a common line, said firstthreaded portion having threads of given height and said second threadedportion having threads of a lesser height; and an externally threadedscrew-type member threadably engaged in said internally threaded bore ofsaid first member, an end portion of said screw-type member beingdeformed so as to freely pass through said second threaded portion ofsaid threaded bore, said deformed end portion abutting at least onethread of said first threaded portion and binding and beingnon-rotatable relative said first threaded portion of said threadedbore.
 2. The biassing device of claim 1 wherein said second threadedportion extends over a greater length of said internally threaded borethan said first threaded portion.
 3. The biassing device of either ofclaims 1 or 2 wherein said deformed said end portion of said screw-typemember comprises a turned down theaded portion.
 4. The biassing deviceof either of claims 1 or 2 wherein the thread height of said secondthreaded portion is approximately one-half the thread height of saidfirst threaded portion.
 5. The biassing device of either of claims 1 or2 wherein the crests of said second threaded portion are substantiallyflat.
 6. The biassing device of claim 5 wherein the thread height ofsaid second threaded portion is approximately one-half the thread heightof said first threaded portion.
 7. The biassing device of either claims1 or 2 wherein the threads of said first and second threaded portionshave substantially the same thread angle.
 8. The biassing device ofclaim 7 wherein said threads of said first and second threaded portionshave substantially the same pitch.
 9. The biassing device of either ofclaims 1 or 2 wherein said threads of said first and second threadedportions have substantially the same pitch.
 10. The biassing device ofeither of claims 1 or 2 wherein said threaded screw-type member is anintermediate screw member having an internally threaded bore, saidinternally threaded bore of said intermediate screw member comprisingfirst and second threaded portions adjacent each other in the axialdirection thereof, said first and second threaded portions of said boreof said intermediate screw member having thread roots which liesubstantially on a common line, said first threaded portion of said boreof said intermediate screw member having threads of given height andsaid second threaded portion of said bore of said intermediate screwmember having threads of a lesser height, and further comprising aninner screw member having external threads thereon and which isthreadably engaged in said internally threaded bore of said intermediatescrew member, an end portion of said inner screw member deformed so asto freely pass through said second threaded portion of said threadedbore of said intermediate screw member, said deformed end portion ofsaid inner screw member abutting at least one thread of said firstthreaded portion of said intermediate screw member and binding and beingnon-rotatable relative to said first threaded portion of said threadedbore of said intermediate screw member.
 11. The biassing device of claim1 wherein said deformed end portion abuts at least a crest of said atleast one thread of said first threaded portion.
 12. The biassing deviceof claim 10 wherein said deformed end portion of said inner screw memberabuts at least a crest of said at least one thread of said firstthreaded portion of said intermediate screw member.